Gamma ray

Gamma rays are high-energy subatomic particles formed either by the decay
of radioactive elements or by nuclear reactions. The wavelength of a gamma
ray is very short—less than the radius of an atom—and the
energy they carry can measure millions of electron volts.

Terrestrial gamma rays—those produced on Earth—are the only
gamma rays we can observe here. A second class of gamma rays, called
cosmic gamma rays, do not penetrate to the surface of Earth because the
ozone layer absorbs high-energy radiation. The only way to detect cosmic
gamma rays, which are created by nuclear fusion reactions that occur
within the core of stars, is by sending a satellite-observatory into
space.

First detection

Cosmic gamma rays were first discovered in 1967 by small satellites called
Velas. These military satellites had been put into orbit to monitor
nuclear weapon explosions on Earth, but they found gamma ray bursts from
outside our solar system as well.

Several other small satellites launched in the early 1970s gave pictures
of the whole gamma-ray sky. These pictures reveal hundreds of previously
unknown stars and several possible black holes, the remains of massive
stars. Thousands more stars were discovered in 1977 and 1979 by three
large satellites called High Energy Astrophysical Observatories. They
found that the entire Milky Way galaxy shines with gamma rays.

The Compton Gamma Ray Observatory

Then, on April 5, 1991, the National Aeronautics and Space Administration
(NASA) sent the Compton Gamma Ray Observatory (CGRO) into space aboard the
space shuttle
Atlantis.
During its nine-year mission, this 17-ton (15.4-metric ton) observatory
provided scientists with an
all-sky map of cosmic gamma-ray emissions, as well as new information
about supernovas, young star clusters, pulsars, black holes, quasars,
solar flares, and gamma-ray bursts. Gamma-ray bursts are intense flashes
of gamma rays that occur uniformly across the sky and are of unknown
origin. The energy of just one of these bursts has been calculated to be
more than 1,000 times the energy that our Sun will generate in its entire
ten-billion-year lifetime.

Words to Know

Antimatter:
Matter composed of antiparticles, or subatomic particles identical to
one another in mass but opposite in electric and magnetic charge. When
an electron (with a negative charge) is brought together with its
counterpart positron (with a positive charge), they destroy each other
and are converted into energy.

Black hole:
The remains of a massive star that has burned out its nuclear fuel and
collapsed under tremendous gravitational force into a single point of
infinite mass and gravity.

Interstellar medium:
The space between the stars, consisting mainly of empty space with a
very small concentration of gas atoms and tiny solid particles.

Nuclear reaction:
The processes by which an atomic nucleus is split (fission) or joined
with another (fusion), resulting in the release of great amounts of
energy.

Ozone layer:
The atmospheric layer of approximately 15 to 30 miles (24 to 48
kilometers) above Earth's surface that protects the lower
atmosphere from harmful solar radiation.

Pulsar:
Rapidly rotating star that emits varying radio waves at precise
intervals; also known as a neutron star because much of the matter
within has been compressed into neutrons.

Quasar:
Extremely bright, starlike sources of radio waves that are the oldest
known objects in the universe.

Radiation:
Energy emitted in the form of waves or particles.

Radioactivity:
The property possessed by some elements of spontaneously emitting
energy in the form of particles or waves by disintegration of their
atomic nuclei.

Radio waves:
Electromagnetic radiation, or energy emitted in the form of waves or
particles.

Solar flare:
Sudden outbursts of light extending from the Sun that last only five to
ten minutes and produce an incredible amount of energy.

Subatomic particle:
Basic unit of matter and energy smaller than an atom.

Supernova:
The explosion of a massive star at the end of its lifetime, causing it
to shine more brightly than the rest of the stars in the galaxy put
together.

Wavelength:
The distance between one peak of a wave of light, heat, or energy and
the next corresponding peak.

A major discovery of the CGRO was the class of objects called gamma-ray
blazars, quasars that emit most of their energy as gamma rays and vary in
brightness over a period of days. Scientists also have found evidence for
the existence of antimatter based on the presence of gamma rays given off
by the mutual destruction of electrons and positrons in the interstellar
medium, or the space between the stars.

NASA decided to end the CGRO's mission after one of its three
gyroscopes failed in December 1999. The observatory, which cost $670
million, could have been kept aloft for eleven more years, but NASA
decided that if more equipment had failed, they could not control its
return to Earth. So, on June 4, 2000, after completing 51,658 orbits of
the planet, the CGRO re-entered Earth's atmosphere and broke apart.
The charred remains of the craft—roughly 6 tons (5.4 metric tons)
of superheated metal—splashed into the Pacific Ocean about 2,500
miles (4,020 kilometers) southeast of Hawaii.

To study gamma rays further, NASA plans to launch the Gamma Ray Large Area
Telescope in 2005.

User Contributions:

Our Universe is in continuous creation formed by the fusion of wave and emission of lightning (electrostatics) and Gamma-ray bursts, the fusion of wave and emission of new Cosmic-ray particles and therefore new hydrogen in space. Magnetized moments, The electromagnetic spectrum is a continuous flow of energy, therefore light is a wave and it is time that is quantized. Quantized within the naked singularity of a blackhole, fused into new moments of time,( An atom mirrors a singularity that mirrors an atom.)

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